Dogs carry their heritage in their size, the coloring and length of their coats, the shape of their muzzles and the length of their ears, just like we do. Greta’s appearance showed that one of her parents was a Labrador retriever. And the other was not. People have guessed that her mix includes anything from border collie to Nova Scotia duck tolling retriever. I never expect to learn what her mom and dad looked like, or what their canine specialties were, but somewhere within Greta is the heart and mind of a hunting dog.

The purebred retrievers we know generally don’t devote much attention to tracking the scents of potential prey. They sniff a little, of course, but then shrug and move on, especially if there’s a ball to be chased, or a training dummy lying invitingly on the grass. Greta wants to chase a ball only if she’s not doing something more important at the moment.

From the outset, Greta loved our weekend walks along a trail that runs over fields, down through a small woods and back up across another field. She couldn’t have told you much about the scenery, since she saw nothing that wasn’t directly ahead at ground level. The first time I took her out on the trail, a rabbit was sitting about 25 feet away from us. It did not move, except for the twitch of its nose. The rabbit watched Greta. She may not have noticed it because it did not move, but she put her nose to the ground and began tracing a twisting path that eventually would lead to the rabbit.

When the trail she had been following brought the dog to within 15 feet of the rabbit, Mr. Bunny decided to move on. Greta caught the flash of his hop and took off, paws pumping, ears and tail flying. The rabbit won, because he was able to duck under a fence to his burrow. But he had to sit and listen to a dog barking, whimpering and digging outside his burrow for 10 minutes.

Greta’s take away lesson was that small animals can be chased. The idea appealed to her. She soon discovered a squirrel munching under the oak tree in the back yard. She began inching toward it, carefully lifting one paw, setting it down gently just a few inches ahead of the weight-bearing paw, checking to see if the movement was noticed before lifting the other paw and setting it down. The squirrel munched on, apparently oblivious. The squirrel apparently enjoyed the game, because it let Greta get within 10 feet of it before scampering up the tree.

Greta and various squirrels have played chase many times since that day. It always ends with her staring up into the branches of the tree. But she knows that someday . . .

The day of the groundhog was a cold, sun-bright day in early spring and Greta and I were hiking our weekend trail. She was about 50 feet ahead of me—she hikes faster than I can—when she spotted the groundhog. She didn’t stop to think about what she would do with a groundhog if she caught one.

The groundhog had gone too far from its burrow in quest of lush grasses to eat. Greta intercepted it and the battle began, dog circling for an opening where she could leap in and bite, groundhog rotating to keep her facing its teeth and claws.

The circling battle continued, dog seeking an opening, groundhog seeking a chance to make a run for home. Greta found an opening, clenched her teeth on the groundhog’s stomach, and hung on. The groundhog scratched at her, but missed. As she clamped down, its strength faded. At the last, it scratched feebly into the air, and was still.

Greta stood, panting. She took an experimental sniff, but did not try to chew into the animal. She would not leave her kill, but she clearly didn’t want to eat it. At last, I put the leash on her collar and led her from the battle scene.

Years earlier, when I described to a veterinarian how one of Greta’s predecessors had killed a groundhog, he said, “Once they get a taste of that, they never quit.”

He may have been right. Greta hasn’t caught a groundhog since that day, but she has never stopped trying.